In a variety of fields, there is a need to maneuver substrates from one location to another. For example, in an automatic computer-to-plate (CTP) exposure machine, unexposed printing plates are robotically maneuvered from an in-feed module to an imaging module to be imaged and, after imaging, maneuvered to an out-feed section.
When the plates are offset plates, suction cups can be used as components of the handling system to move the plates from one location to another.
Flexographic printing plates have gained favor in the industry because of their superior durability and the environmentally friendly nature of the plate processing and the ink used on the printed media. Due to the presence of a delicate photopolymer resin layer on the top surface of flexographic printing plates, however, handling these types of printing plates can be a concern. Standard suction cup type handling systems would mar the photopolymer resin layer.
U.S. Pat. No. 6,425,565, hereby incorporated herein by this reference, discloses a suction cup covered by an aperatured flexible sheet in an attempt to provide a conformal barrier which prevents direct physical contact between the plate and the contact flange of the suction cup. Still, due to the contact between the plate and the suction cup, the possibility for scratching, marring, or damage still exists.
Also, flexographic printing plates stacked together are separated from each other by a paper interleaf or slip sheet which must be removed before imaging. Thus, there is a need to not only carefully handle the flexographic printing plates but also the requirement that the slip sheet between any two plates be removed by the handling system before imaging.
The removal of slip sheets from flexographic plates is more complicated than conventional offset plates due to the tacky nature of the soft photopolymer coating. The flexographic photopolymer can be very soft and tends to cold flow causing the slip sheet to adhere strongly across the surface of the plate especially near the edges. This increased adhesion sometimes prevents the slip sheets from being removed solely by the more common simple removal methods such as an airjet blow off system. So, there is a need for a mechanism to reliably separate the slip sheet from the flexographic plate.